In the process of injection molding, a heavy metal mold is used to contain the pressure of the fluid plastic material. The mold halves are positioned in the injection molding machine and held in guide rails by suitable clamps. In view of the heavy weight of the mold, it is difficult to place the mold into the injection molding machine and to remove the mold from the machine when the machine is to be used to form a different part. If the mold is not raised and lowered carefully in the guide rails, the mold will tend to bind against the rails and, in view of the heavy weight, become very difficult to move without damaging the mold or the injection molding machine.